At least 55 people have been killed in fierce fighting that erupted in western Uganda between security forces and a separatist militia linked to a tribal king, police said Sunday.

Police spokesman Andrew Felix Kaweesi said 14 police officers and 41 militants had died in the clashes in the town of Kasese on Saturday, when fighters linked to the royal guard of the Rwenzururu kingdom attacked patrolling security forces.

"Yesterday a joint Uganda police and UPDF (army) operation, patrolling in Kasese town... came under attack by Royal Guards of the kingdom. The attackers threw an improvised grenade which exploded and injured one soldier. Security forces reacted and shot in self-defence, killing four attackers," said Kaweesi.

"That incident set of an explosion in all local sub-counties. Fighting continued from morning to late evening."

Kaweesi said the attackers -- not all of whom were royal guards -- had guns, spears and improvised explosive devices.